The Jekyll Island Authority is dropping out of a controversial beachfront development deal because its private partner could no longer guarantee a timeline for completion. The authority and Atlanta-based Linger Longer LLC had been renegotiating timing and financial terms of the package, which called for building two hotels, condominiums and time-share units, and up to 30,000 square feet of retail space. But the authority still wanted a firm timeline for completion of each component, a spokesman said, and Linger Longer couldn’t make it so.